Multi-functional filtering medium

ABSTRACT

A filtering medium is economically produced by treating a highly humified peat source with an alkaline solution followed by mixing with a quaternary amine compound until the humic and fulvic acids have precipitated. A filter cake is formed from the residue by various means including acid oxidation, heating with or without acid reagent or by semi-coking to produce a final dried product having excellent filtering properties for hydrophobic compounds, as well as ion-exchange capacities for both anions and cations from aqueous solution.

This application is a divisional application of Ser. No. 856,368, filed28 Apr. 1986, now U.S. Patent No. 4,778,602, for MULTI-FUNCTIONALFILTERING MEDIUM AND METHOD OF PRODUCING SAME, invented by Ralph S.Allen.

This invention relates to filtering media and to methods of producingsame; and more particularly relates to a novel and improved multipurposefiltering medium composed of chemically modified peat material for thefiltering of hydrophobic, anionic and cationic solubilized compounds andto novel and improved methods of producing same.

BACKGROUND AND FIELD OF THE INVENTION

Peat is commonly used as a filtering medium, both in its raw state aswell as in a form which has been chemically treated from its parentmaterial; yet, its application is severely limited by certain inherentcharacteristics of the material itself. For example, raw peat isphysically quite restrictive to the flow of liquid or effluent to befiltered. In addition, it contains fulvic acid which as a solublefraction can contribute to soluble organic contamination and thusincrease the biological oxgen demand; also this soluble organic fractionhas been shown to react with chlorine to produce chlorinated organiccarcinogens.

Many forms of chemically modified peat have been developed and proposedfor use as water filtering media. Activation of peat, either byair-oxidation or wet-oxidation methods, results in the formation of amedium similar to certain activated charcoals that are capable ofremoving hydrophobic compounds from aqueous solutions. Unlike theactivated charcoals, the chemically modified peats have the capacity toremove heavy metal cations from the filtrant. Nonetheless, these peatmaterials have several limitations in terms of preparation costs, theirtendency to chip and shed; and more importantly, have serious chemicallimitations, such as, swelling and leaching of organic matter in thepresence of alkaline or detergenated solutions.

Synthetic ion-exchange resins which incorporate an inert matrixmaterial, such as, polystyrene or other plastics include an active agentwhich can exchange a cation for a less desirable cation, or an anion foranother anion. These resins, however, are so costly to manufacture thatthey are generally much too expensive to be used in industrial orcommercial applications on a large scale basis. All ion-exchange resins,while useful for cation and anion exchange, have no significantcapability for removal of hydrophobic compounds.

U.S. Patent No. 4,459,149 to E. F. Moran et al is directed to a processfor treating humus material including peat which in a intermediate stageof its process forms a dry filter cake which is then converted to ahumate salt or to a humic acid; the patent is essentially concerned withthe formation of humic substances for agricultural purposes but not tobe the fomation of a filtering medium as an end product. U.S. Patent No.3,328,158 to A. L. Marks is directed to the preparation of organicfertilizer by combining nutrient materials with a readily soluble humicacid, such as, peat and of solubulizing materials by a pressurizedcooking process followed by the addition of selected calcium-magnesiummaterials together with nitric acid and phosphoric acid. Otherrepresentative patents are U.S. Patent No. 2,093,047 to J. Wageningen etal; No. 2,158,918 to C. S. Townsend et al; No. 2,317,990 to E. F.Grether; No. 2,992,093 to E. M. Burdick; No. 3,321,296 to R. Abbe; No.3,398,186 to N. N. Schwartz; No. 3,603,643 to M. Hirota et al; No.3,617,237 to S. Nagasawa et al; No. 3,674,649 to M. Formisano et al; No.3,770,411 ato J. C. Chambers et al; and No. 4,223,449 to W. Bodle et al.

It is proposed in accordance with the present invention to provide for anovel and improved multi-purpose filtering medium which is specificallyadapted to use in water and possibly air filtration in which a peatsource is chemically modified in such a way as to greatly enhance itsfiltering capabilities. More specifically, a method of producing afiltering medium from a peat source is proposed which is economical,suitable for high volume production, and capable of producing a materialwhich is stable with high ionic exchange rates and hydrophobicabsorpotion over a wide pH range.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide for anovel and improved filter medium and to a method of making the same froma chemically modified peat source in an economic and reliable manner.

Another object of the present invention is to provide for a novel andimproved filtering medium specifically adaptable for use in filteringwater which is resistant to alkaline solution leaching, possesses bothcation and anion exchange capacities, has a density greater than water,is extremely hard and demonstrates excellent flow characteristics incolumn and fluid-bed systems.

A further object of the present invention is to provide for a novel andimproved filtering medium which does not swell in solution or leachorganic matter into aqueous solutions or otherwise break down and leachorganic composition compounds over a wide pH range when used as a waterfiltering medium.

It is an additional object of the present invention to provide afiltering material having a hard carbon dense nature which resistsphysical breakdown in different environments, has hydrophobic absorptioncapacity so as to lend itself well to removal of hazardous organicsubstances, is biodegradable, but can be made to be bacterial static orgermicidal as required through chemical alterations and is non-toxic.

A still further object of the present invention is to provide for anovel and improved method of making a filtering medium from a peatsource which is cost-effective to produce both in terms of productionand material costs and procedures and is conformable for use in smallbatch as well as mass production operations.

In accordance with the present invention, an all-purpose filteringmedium has been devised which is composed of a chemically modified peatsource in which the humic and fulvic acid fractions thereof are "locked"into the resultant heterogenous structure. The structure has a densitygreater than 1.0 with a hardness and stability such that it can beground to the desired mesh size to operate as an effective filteringmedium over extended time periods without undergoing changes in itsphysical and chemical characteristics. The method of producing thefiltering medium of the present invention is characterized by the stepsof intermixing a highly humified source of peat into an alkaline aqueoussolution for a time period sufficient to solubulize the humic and fulvicacid fractions of the peat, introducing a quaternary amine compound intothe solution in an amount sufficient to precipitate the humic and fulvicacid fractions, followed by removing the solid residue including thehumic and fulvic acid fractions and drying same into a hard dense filtercake.

Various steps may be practiced in the drying or dehydration of the solidresidue including but not limited to treating by acid oxidation, heatingwith or without acid reagents or by semi-coking. The preferred treatmentis a semicoking procedure in which the residue is placed in a closedcontainer under pressure and heated into the range of 200° C.-1000° C.,thereby reducing oxidation of the residue and increasing its porosity.Heating under pressure is continued for a period of four to five hoursor longer until the material has hardened but has not reached completedryness. The resultant material is in the form of a hard cake which canbe ground into particles of the desired mesh size.

The above and other objects, advantages and features of the presentinvention will become more readily apparent than the following detaileddescription when taken together with the accompanying drawings, inwhich:

FIG. 1 is a flow diagram illustrating the steps followed in a preferredmethod in accordance with the present invention;

FIG. 2 illustrates a typical application of the filtering medium of thepresent invention in a column flow application; and

FIG. 3 illustrates another typical application of the filtering mediumof the present invention in a fluid bed filtering system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, there is shown by way of illustrative examplein FIG. 1 the preferred process of the present invention in which a peatsource designated at 10 is stirred into an alkaline aqueous solution tosolubilize the humic and fulvic acid fractions as designated at 12. Theresultant solution is mixed at 13 with dimethyldi (hydrogenated-tallow)ammonium chloride in order to precipitate all soluble fractions out ofthe solution. The solid matter is then removed from solution at 14 andactivated by a semi-coking procedure as represented at 16. The resultantproduct forms an extremely hard cake which can be ground to the desiredmesh size as at 18. Any fines can be recycled back through the system asrepresented at 19 or used as a surface active oil coagulant. Thefollowing is a typical series of chemical reactions which take place inthe process of the present invention:

The reaction of an organic acid with that of a base must be examined inorder to understand how the organic "salt" product of this reactionbecomes soluble in water. First of all, organic acids in general arevirtually insoluble in aqueous solutions due to a lack of ionic charge;however, when these same organic acids are reacted with a base, theybecome highly charged to produce the deprotonated salt form. Forexample: ##STR1## and this mechanism works precisely in the same mannerfor the organic fractions of peat which display a high polyacidic groupcharacter, i.e., fulvic and humic acid fractions.

On the other hand, when the quaternary amine is added to an alkalinesolution, where both the fulvic and humic acid fractions are solubilizedin salt form, the following reaction takes place: ##STR2## wherein R' isa lipid or tallow and R is a carbon backbone containing multi-functionalgroups as a part of the humic macro-molecular structure. The finalproduct of this reaction has once again lost its charged ionic natureand thus becomes hydrophobic or water insoluble.

Not all of the acidic reactive groups are "coupled" with the quaternaryamine but rather just enough of these sites are reacted to prevent thesolubilization of the molecule under strong alkaline conditions.

Highly humified peat in its raw state may be generally characterized ashaving lost much of its distinctly or highly fibrous plant materialremains, thus containing considerable amorphous material content. Ingeneral, peat as a humic substance can be divided into three mainfractions: (a) humic acid which is soluble in dilute alkaline solutionsbut which can be precipitated by acidification of the alkaline extract;(b) fulvic acid which is the humic fraction which remains in theacidified solution and is soluble in an acid or base; (c) the humicfraction that cannot be extracted by a dilute base or acid and iscustomarily referred to as humin. Humus-containing matter may besubdivided into three main components; namely, non-humic organic, humicsubstances and inorganic material. The humic substances consist of thefulvic acids, humic acids and humin. In the preparation of the filteringmedia, peat is the humic substance of choice in that it constitutes asubstantially pure source of humic or organic matter due to its lowcontent of mineral matter and its high content of decomposed organicmatter.

For the purpose of illustration and not limitation the following peatsamples were found to exhibit favorable characteristics in thepreparation of the filtering medium:

(a) Irish peat was obtained from a blanket bog at a depth of 3.5 feetfrom the Agricultural Institute, Peatland Expermental Station, Glenamoy,Co. Mayo, Ireland. The peat appeared dark brown in color with a highcontent of amorphous solids (i.e. nonfibrous material), yet, somedistincly fibrous plant remains could be visually detected. Thus, thissample represents a highly `humified` source i.e. advanced degree ofdecomposition.

(b) Colorado peat wass obtained from Guanella Pass, Colo. at an alitudeof 11,669 feet above sea-level at a depth of 1 foot below the surface ofthe bog. Plantlife in the surrounding area, high above timberline,consisted mainly of mosses, lichens, some grasses and alpinewildflowers. The peat was highly fibrous with little observableamorphous material content. It appeared medium brown in color and notnearly as compacted as that of the Irish peat.

(c) Canadian Sphagnum was commercially purchased from the Fafard PeatMoss Company of Shippegan, N.B. This sample appeared to have the highestfibrous content with readily observable plant tissues and very littleamorphous content could be recognized. It was a very light tan in colorand crumbled easily to the touch.

EXAMPLE 1

10 grams of a highly humified peat in its raw state, preserved in anaturally moist condition, is vigorously stirred into 100 ml of 0.5Msodium or potassium hydroxide for a period of approximately one hour. Tothis solution an industrial grade quality quaternary amine compound isadded with continuous mixing until all of the solubilized organic matterconsisting essentially of the humic and fulvic acid fractions haveprecipitated. This is accomplished with varying amounts of quaternaryamine to approximately 0.95 grams depending upon the peat sourceselected, its moisture content, and the specific quaternary compoundselected. The remaining insoluble residue is collected either bycentrifugation at moderate speeds up to 2700 rpm or by passing themixture through coarse filter paper, such as Whatman #41, under lowvacuum.

The moist cake is transferred to an evaporating dish and 20 ml ofconcentrated reagent grade nitric acid or sulfuric acid is added. Theevaporating dish is placed upon a hot plate, and the temperature israised until the aqueous acid solution is visually observed to beginfuming typically at a temperature on the order of 200°-250° C. Thisprocess is allowed to continue until all of the acid solution hasevaporated to dryness leaving only a hard cake residue. The cake is thenground to the desired mesh size. The fines may be recycled back throughthe system with a fresh batch to minimize waste.

The use of oxidizing acids helps to create a better cation exchangematerial displaying an improved capacity to remove metal cations fromaqueous solution. The use of such "fuming acids" in the preparationprocess, however, not only requires specialized handling and equipmentbut also could be a source of toxic air pollution. In addition, theadded expense of acid oxidation makes the technique in this example oflimited cost effectiveness.

EXAMPLE 2

The solubilization and precipitation steps as described in Example 1 arefollowed by the additional step of adding an inert material such as, awashed sand of uniform mesh size along with the addition of the acidprior to the evaporation step described in Example 1. The mixture mustbe periodically stirred while heating to insure even coating of theparticulates with the chemically treated peat medium. This modificationserves to reduce the cost of the final product by coating it upon theinert material so as to increase the surface area of the filteringmedium. Any residual fines may be recycled back through with a freshbatch to minimize waste.

This modification of Example 1 serves to increase product quantitywithout the addition of expensive reagents. Thus this added inertmaterial does address in part the problem of the high cost of producingthe filtering medium. Otherwise, it suffers the same fuming acidhandling and cost effectiveness problems as Example 1.

EXAMPLE 3

Following the initial preparation procedure and the collection of thefiltering cake, described in Example 1, the residue is allowed toair-oxidize in an oven at 250°-300° C. for 24 hours without the use ofthe oxidizing acid reagents. The cake is then ground to a desired meshsize. Again, the fines may be recycled back through with a fresh batch.

By eliminating the need for the oxidizing acids, the cost of producingthe filtering medium is reduced. The charring process using this method,however, is difficult to control and is often uneven, resulting in aheterogeneous end product lacking uniformity in both chemical andphysical properties. Further, complete drying of the medium renders ithydrophobic thus making it very hard to re-wet.

EXAMPLE 4

The procedure followed in Example 1 is performed in the absence ofatmospheric oxygen by placing the mixture of the residual peat cake andthe oxidizing acid into a covered pyrex dish and heating at 250°-300° C.for extended periods of time (upwards of four to five days). Thismodification to the previous procedure does not allow for the rapid lossof moisture, nor does it allow prolonged exposure to atmospheric oxygen.The cake is then ground to a desire mesh size. The fines may be recycledback through the procedure with a fresh batch to minimize waste.

This modification avoids the complete dessication of the final product.The heating of the cake for several days, however, is not very costeffective.

EXAMPLE 5

The solubilizing and precipitation steps of Example 1 are followed. Theresidue is placed into a closed container where a pressure of 40 psi isgenerated by heating the moist material to 200° C.-1000° C. Heatingunder pressure is continued for approximately four to five hours orlonger until a very hard material is formed but which has not gone tocomplete dryness. The cake is then ground to a desired mesh size. Asbefore, fines may be recycled back through the procedure with a freshbatch to minimize waste.

The last Example produces an outstanding final product without therequirement of using oxidizing fuming acids, excessive long heating orair oxidation. Quality control is maintained by combining heating andpressure control. By adding an inert material, as in Example 2, to theresidue, it is possible to produce a high quality medium capable ofremoving organic hydrocarbons, metal cations and toxic anions fromwater. It is found that a concentration of 40% quaternary amine(dimethyl-dihydrogenated beef tallow) ammonium chloride by weight withhighly humified peat will produce a filtering medium having 0.172 meq/gmor Na⁺ cation exchange while displaying hydrophobic absorption capacityas well as alkalinity resistance to 13.4 pH for solubilization of theorganic matter. A lower concentration of 10% quaternary amine by weightwith 90% peat results in a filtering medium having 0.42 meq/gm in Na⁺cation exchange with somewhat lower alkaline leaching resistance, up topH 10.8, and a lower hydrophobic absorption capacity.

The following is a detailed breakdown of the experimental results fromthe foregoing Examples 1 to 5 using milliequivalent/gm as a standardmeasure for Sodium (Na⁺) cation exchange capacities:

                  TABLE I                                                         ______________________________________                                                                           Exchange                                   Peat                QA/Peat Weight (gm)                                                                          Capacities                                 Type      QA Used   (Dry Weight)   (meg/gm)                                   ______________________________________                                        EXAMPLE 1:                                                                    Canadian                                                                      Sphagnum  1         0.94/10.1      ND                                         Canadian                                                                      Sphagnum  2         0.95/10.0      0.041                                      Canadian                                                                      Sphagnum  3         0.98/9.9       0.067                                      Irish Peat                                                                              1         0.93/10.2      ND                                         Irish Peat                                                                              2         0.86/9/8       0.54                                       Irish Peat                                                                              3         0.95/10.2      0.69                                       Colorado Peat                                                                           1         1.03/10.5      ND                                         Colorado Peat                                                                           2         0.99/10.0      0.13                                       Colorado Peat                                                                           3         0.98/10.2      0.20                                       EXAMPLE 2:                                                                    Irish Peat                                                                              3         0.92/10.0      0.38                                       EXAMPLE 3:                                                                    Irish Peat                                                                              3         1.03/9.8       0.24                                       EXAMPLE 4:                                                                    Irish Peat                                                                              3         0.97/10.0      0.67                                       EXAMPLE 5:                                                                    Irish Peat                                                                              3         0.95/9.9       0.42                                       Irish Peat                                                                              3         3.98/10.0      0.172                                      ______________________________________                                         Notations:                                                                    ND = Not determined                                                           QA#1 = dimethyldicocoa ammonium chloride                                      QA#2 = dimethyl (hydrogenated tallow) benzyl ammonium chloride                QA#3 = dimethyldi (hydrogenated tallow) ammonium chloride                

From Example 1, Canadian Sphagnum has the least degree of decomposition,followed by Colorado Peat and then Irish Peat. That is to say, as theorganic matter displays a greater degree of decomposition, the materialwill also have a greater number of phenoxy and carboxylic functionalgroups per gram of material. These functional groups (i.e., R--OH andR--COOH) represents those groups most responsible for cation exchangewith an acidic proton "H⁺ ".

When a given quaternary amine is used within the same method ofpreparation, while varying only the peat source, it can be seen that themore decomposed (i.e., humified) the peat, the greater the cationexchange capacity of the final filtering medium.

Another trend found within this set of data establishes that thequaternary amine of choice determines the degree of cation exchangecapacity of the final medium. Not only does dimethyldi(hydrogenatedtallow)ammonium chloride produce a final medium with a greater cationicexchange capacity over that produced with dimethyl (hydrogenatedtallow)benzyl ammonium choride, but it is approved by the FDA as a foodadditive having little known toxicity to laboratory animals and isbiogradable. For these reasons, all additional tests utilized only IrishPeat and the dimethyldi(hydrogenated tallow) ammonium chlorideexclusively, while changing parameters of preparation in the followingExamples.

Referring to Examples 2 to 5, having established which quaternary amineand peat source is best, certain changes in preparation parameters wereexamined with the dual objective of minimizing cost of preparation whileeither maintaining cation exchange capacity or increasing it. Withrespect to the various advantages or disadvantages of each preparationmethod, as it addresses the foregoing goals, these have been describedpreviously.

However, Example 5, which does not require the use of oxidizing acids,was taken one step further. In one case, the Irish Peat was treated withapproximately 10% of quaternary amine to peat while in the second casethe medium was prepared with nearly 40% quaternary amine to peat (weightof quaternary reagent to peat on a dry basis). While the medium preparedwith the lesser weight percentage of quaternary amine displayed agreater cationic exchange capacity than did that of the higherquaternary concentration, the higher quaternary concentration medium wasable to resist pH leaching of organic material up to 13.4, whereas themedium using the lesser quantity of quaternary amine was only able toresist leaching up to a pH of 10.8. For the most part, the 10%quaternary amine treated peat would be satisfactory for all purposesexcept that of filtering aqueous solutions of extremely high alkalinity.This would be a rare requirement where an effluent would exceed a pHgreater than 10.8; and, even if this requirement should exist, then thesolution could be acidified to a pH within operating range of themedium.

The filtering medium (Example 5, 10% quaternary amine to peat) wasplaced in a 50 ml buret (approximately 1.97 gm medium by dry weight)with a small wad of glass wool placed at the base, and covered with aclean washed sand at the top of the column. The buret was filled withde-ionized water and the air bubbles within the pores of the medium wereremoved under a vacuum.

The 50 ml solutions of selected model dyes were allowed to pass throughthe filtering medium at a rate of 10 ml per minute. Those dyes selectedwere toluidine blue, methyl red and sudan II because of their similarityto commonly used pesticides. Concentrations of the dyes were notinitially quantified; however, enough of each were dissolved to producehighly colored solutions. The resulting concentration of the effluentswas to be spectroscopically analyzed to determine the compoundconcentration of "unabsorbed" fraction not taken up by the filteringmedium. However, in each case, all of the dye was removed from thesolutions.

The filtering medium described herein does not suffer from many of theeconomic, physical, or chemical limitations of the filtration media incommon use today. This filtering medium has been found to have none ofthese restrictions and, in addition, displays many desirablecharacteristics including removal of organic compounds, heavy metalcations, and anions over a wide range of pH. These suggest the abilityto be used as a cost-effective, multi-purpose media for all applicationswhere pure water is required.

Specifically, the invention has been shown to have the followingcapabilities as a universal filtering medium:

1. Removal of model organic compounds representing hazardous hydrophobicorganic compounds from aqueous solutions (e.g. herbicides, pesticides,polychlorinated bipenyls, etc.).

2. Removal of toxic anions (such as NO₃ ⁻, No₂ ⁻, I⁻, Br⁻, etc.) fromaqueous solutions by ion exchange with chloride (Cl⁻).

3. Removal of heavy metal cations from aqueous solution by ion-exchangewith protons (H⁺), e.g., Hg⁺, Pb⁺. Se⁺, Cd⁺. etc.

Other desirable characteristics of this invention are the following:

1. Has a density slightly greater than 1.0, thus can be readily used incolumn packed apparatus, or submerged in aqueous fluid bed filteringapparatus.

2. Is extremely hard and carbon dense which does not swell and whichrenders it very resistant to chipping, scaling, or shedding underturbulent conditions, such as, found in fluid bed filtering apparatus.

3. Can be incinerated for either disposal of toxic hydrocarbons orrecovery of rare metals from the ash.

4. Is biodegradable by common soil bacterium, thus allowing for thechemical breakdown of many hazardous hydrocarbons by means which do notcontribute to air pollution. At the same time, if desired, it can beprepared to be bacterial static or bacterial cyctotoxic by theincorporation of organic germicides, e.g. benzyl derivative quaternaryamines, or inorganic germicides, e.g., silver nitrate within the matrixof the medium compound.

5. Does not leach organic matter into the aqueous solution over a widerange of pH from 0 to 13.4.

6. Is prepared from parent materials that are virtually non-toxic, e.g.,peat and an FDA approved food additive made from beef tallow, thussuggesting its applicability in purification of drinking water andpossibly in de-toxification of the human digestive tract by removal ofingested heavy metal cations and/or hazardous hydrocarbons.

The following suggests some of the practical applications of thefiltering medium of the present invention: (a) Column flow "in line"household water filtering for removal of undesirable organics, heavymetals and anions; (b) Portable filtration system for field use;Filtration of brackish, poisoned or polluted water to produce potabledrinking water, particularly valuable for military and others whereclean drinking water is not available; (c) Treatment of municipal watersupplies to remove organics, heavy metals, and anions; (d) Tailings-pondtreatment of mining and/or industrial effluents by sedimentationagitation of filtering media; and (e) Waste water treatment of municipalsewage at the tertiary stage to remove residual contaminants. Thefiltering means of the present invention demonstrates the ability orcharacteristics to have potential application for removal of toxicmetals as well as hydrocarbons from the intestinal tract by ingestion ofthe filtering medium; also the removal of oil from water surfaces, suchas, oil spills by sprinkling the finely powdered filtering media. In thelatter application, oil will be absorbed before the medium becomeswetted, following which the contaminated means will settle to the bottomof the water body thereby holding the oil and becoming part of thebottom sediment. Other potential applications include the recovery ofrare or valuable metals from leachate solutions and the filtration oftoxic dust and gases from air.

There is illustrated in FIG. 2 one practical application of the presentinvention to a column flow apparatus wherein the filter medium M ispacked into a cylinder 20, opposite ends of the cylinder being closedexcept for inlet port 22 at one end and an exhaust or exit port 24 atthe opposite end. A retaining screen 25 is positioned across the exitend of the cylinder. The incoming effluent is introduced through theinlet port 22 and, upon filtering by passage through the tightly packedfilter medium M, will exit directly through the port 24. In the columnflow application, preferably the filtering medium is ground to a meshsize on the order of 350-500; however, mesh size may be varied as perflow and filtering requirements.

FIG. 3 illustrates another form of filtering apparatus in which thefiltering medium M is packed into a cylindrical casing or canister 30having a retaining screen 32 extending horizon tally across a lowersegment of the cylinder. In this particular application, customarilyreferred to as a fluid bed, an inlet port 34 is positioned at one end ofthe container adjacent to its upper peripheral edge and an exit port 36at the opposite end adjacent to its lower peripheral edge. The fluid bedapparatus as described has an advantage over a column flow or in linecanister in offering the least resistance to flow of the fluid medium tobe filtered and thus smaller particle sizes may be used in theconstruction of the filter medium in order to achieve greater surfacecontact with the solution or liquid medium to be filtered. The fluid bedapparatus generally can be expected to be more expensive, occupy alarger area than a column flow apparatus and requires more labor inreplacing the filtering medium as it becomes spent.

Although activated carbons have been around for centuries, those whichare made from "carbon-dense" materials, such as, hardwoods, coal andcoconut shells have only trace cation-exchange capacities on the orderof less than 0.06 meg/gm. Yet, "activated" carbons made from thesesubstances display excellent hydrophobic absorption capacities (i.e.,hydrocarbon compounds) and are highly resistant to chipping or sheddingunder turbulent conditions. Activation of peat, however, yields aproduct displaying both a high cation-exchange capacity and an excellenthydrophobic absorption capability. While activated carbons made frompeat have the desirable advantage of cation-exchange over those madefrom carbon-dense materials, they are subject to shedding, chipping andcan be easily crushed under stress. In addition, these peat-derivedactivated carbons all release, or leach, organic matter (i.e., humic andfulvic acids) into aqueous solutions of pH 8.0 or higher thus causing acontamination problem in itself.

The quaternary amine treated peat displays all the advantages of the"carbon-dense" activated media in terms of hydrophobic absorptioncapabilities and physical characteristics; yet it possessescation-exchange capacities found in activated carbons made from peatwithout the disadvantages of alkaline leaching or swelling.

To a large extent, porosity is directly related to surface area. Thus,where the greatest porosity can be achieved, the maximum "exposure" ofthose functional groups to the solution containing the species which isto be removed can be realized. In this respect, a toxin will have anincreased chance of coming into contact with the chemically active groupupon the filtering medium, thereby increasing its chances for reactingwith that specific group on the surface of the filtering medium. While amaximum surface area may sound ideal, this must be counterbalancedagainst creating a weak solid matrix subject to physical breakdown(i.e., chipping, shedding, crumbling, etc.). Generally, the length ofcoking under pressure and heat determines to what degree the organicmedium undergoes thermal decomposition and thus vaporization of bothsurface and internal constituents in "opening up" the solid matrix.

It is therefore to be understood that various modifications and changesmay be made in the method and resultant product formed in the presentinvention without departing from the spirit and scope of the presentinvention as defined by the appended claims.

I claim:
 1. A filtering medium having hydrophobic properties togetherwith anionic and cationic exchange capacities, said filtering mediumcomposed at least in part of heat activated humic and fulvic acidfractions and produced from the steps of:(a) mixing a source of peat inan alkaline aqueous solution until the humic and fulvic acid fractionsin the peat are solubilized; (b) precipitating said humic and fulvicacid fractions from said peat and alkaline aqueous solution byintroducing into said solution a quaternary amine and mixing for a timeperiod sufficient to precipitate said humic and fulvic acid fractionstherefrom; (c) removing said humic and fulvic acid fractions from saidsolution; and (d) activating said humic and fulvic acid fractions soremoved to a substantially dry state by heating at an elevatedtemperature in a closed, pressurized container for a time periodsufficient to dehydrate said fractions to a substantially dry state,said closed, pressurized container being pressurized to a pressure levelon the order of 40 psi.
 2. The filtering medium according to claim 1,wherein said filtering medium has a mesh size on the order of 350-500.3. The filtering medium according to claim 1, in which said quaternaryamine is a dimethyl dyhydrogenated tallow ammonium chloride introducedin the ratio of 10 to 40 parts of quaternary amine to 100 parts by dryweight of said peat.
 4. The filtering medium according to claim 1, saidmedium have a cationic exchange capacity of at least 0.40milliequivalent/gm.
 5. The filtering medium according to claim 1, saidmedium having a density greater than 1.0 and capable of resisting pHleaching of organic material in the alkaline range up to 13 pH.